Combustion within an engine produces heat and a flow of chemical by-products as an exhaust gas flow. Various methods exist for modulating the combustion process to improve fuel efficiency and control exhaust gas emissions. One important property used to monitor the combustion process and the aftertreatment of the exhaust gas flow is the exhaust gas temperature. Temperature sensors are well known for monitoring temperature in a gas flow. However, temperature sensors measure the temperature of the temperature sensor and not the temperature of the gas flow. Heat energy must flow between the gas flow and the temperature sensor for temperature changes in the gas flow to be measured. This resulting temperature response in the temperature sensor to the flow of heat energy introduces a delay or lag relative to temperature changes in the gas flow. Additionally, the temperature of the temperature sensor is a result or a summation of historical heat flows. This summing or averaging effect upon temperature sensor temperatures masks high speed or alternating changes in temperature in the gas flow, reducing the sensitivity of the temperature sensor readings. Results of the lag and averaging errors of temperature sensor readings in an exhaust gas flow include compromises in engine control and management of exhaust gas aftertreatment.